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<br />76 <br /> <br />Parasites <br /> <br />The functional group termed parasites ;lncludes those organisms with <br />roorpho-behaviO,x:sl adaptations for the internal and extE!rnal survival of <br />eggs, larv'ae 'and pupae, prepupae and pupae :In cocoons and pupal cases. The <br />dominant food type is living animal tissue .~nd the genE!ral particl,~ size <br />range of food is in excess of 1 mm. Dominant members of parasites are <br />found in the insect orders Coleoptera and Hymenoptera. <br /> <br />Food Resource and P,:ocessing <br /> <br />The term processing describes the fate of particulate organic matter <br />(POM) and dissolved organic matter (DOM) and similar mclterials produced in <br />streams. Peterson and Cummins (1974) dividE!d organic matter degradation <br />into short-term physical processing consisting of leaching (i.e., <br />extraction of DOM by water) and long-term biological processing by microbes <br />.and invertebrates. In each case the materials are processed (degraded) to <br />carbon dioxide and nutrients. Portions of the breakdo.'n products become <br />bound up for varying periods in resident members of the community (standi:1g <br />crop) and the remainder are exported downstream. <br /> <br />Short-Term Processing (Leaching) <br /> <br />Short-term processing of POM mayor ma)' not begin prior to its stream <br />entry. Thus the amount of DOM produced from POM may depend on the <br />preconditioning of the CPOM in the riparian or terrestrial environment. <br />Once CPOM in the form of leaves, needles, t.'igs, bark, flowers, fruits, <br />etc. enters a stream it readily releases soluble components by the process <br />of leaching. The majority of leaching occurs within 24 hours of initial <br />wetting regardless of water temperature (Peterson and Cum:nins 1974). A 5 <br />to 30 percent loss in the dry weight of leaf litter occurs during the first <br />day and rate is a function of leaf species (Cummins et al. 1972). Thus a <br />rapid and pronounced loss of dry weight during the first 24 hours Is <br />followed by a long period, sometimes lasting many months, of gradual weight <br />loss. <br /> <br />Long-Term Processing (Kicrobiota and Invertebrates) <br /> <br />Long-term processing of CPOM is related to the degree of terrestrial <br />preconditioning and the temperature regime (Cummins 197,,). The degree of <br />terrestrial colonization of CPOM by fungal hyphae and spores at war;n summer <br />temperatures can playa significant role in processing. CPO~!, upon entry <br />to stream systems, becomes rapidly colonized by bacteria cells and spores, <br />aquatic hyphomycete fungi, protozoans, etc. Significant. colonization <br />occurs in the first week or two depending on the degree of terrestrial <br />conditioning. Before, during, and following this colonization period CPO~ <br />is degraded to FPOH by water turbulence, leac:hing (solubilization), <br />mechanical disruption by physical abrasion, Dlicrobial me,tabolism and animal <br />feeding. The rate of degradation or conversIon is dependent on the <br />terrestrial preconditioning, the qualitative characteristics of the CPOM <br />and temperature. Different leaf species undE,rgo conside,rably different <br /> <br />~ <br /> <br />~'~'~~lal' <br />